Intel Kaby Lake G Core i7-8705G review: Why Nvidia should be scared
Intel's combination of Core i7 and Radeon RX Vega exceeds performance expectations and represents a future threat to Nvidia.
By Gordon Mah Ung
PCWorldJun 14, 2018 3:00 am PDT
Kaby Lake G’s marriage of Intel CPU and AMD GPU is an unusual partnership in the spirit of peanut butter and chocolate, R2-D2 and C3PO in Star Wars, and yes, even Tom Hanks and the dog in Turner and Hooch. People love the unexpected.
Built out of an Intel 8th-generation quad-core CPU and an AMD custom Radeon RX Vega M graphics chips, Kaby Lake G shook the PC industry when Intel announced the chip at CES. After putting Kaby Lake G through the wringer via HP’s Spectre x360 15, it’s now clear to us that this new CPU/GPU combination may very well represent the future of the PC and deserves the fear it’s generating among competitors.
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HP Spectre x360 15 (2018) with Kaby Lake-G
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What is Kaby Lake G?
When Kaby Lake G was first announced, many assumed Intel had contracted with AMD to replace its own graphics cores on the CPU die. In fact, the module houses an Intel CPU with Intel integrated graphics along with an AMD Radeon RX Vega M GL graphics chip and memory.
Rather than connect the chips using traditional methods, Kaby Lake G does it all with Intel’s Embedded Multi-Die Interconnect Bridge (EMIB). Intel says its EMIB costs far less than competing techniques for connecting multiple dies and is far easier to implement as well.
On Kaby Lake G, a conventional x8 PCIe 3.0 connection joins the CPU to the GPU. Intel uses its EMIB to connect the custom Radeon graphics core with 4GB of HBM2 memory.
The resulting module is a whole lot smaller and thinner than a traditional setup. Kaby Lake G also offers more fine-grain power control of the components. With a traditional separate CPU and GPU, one part doesn’t know what the other is doing. It’s really up to the laptop maker to manage it all.
With Kaby Lake G, the power and thermal needs of the CPU, GPU, and the RAM for the GPU are all managed as one. If the module’s under a heavy graphics load, the CPU can back off. If the CPU is under a heavy load, the GPU can back off. That initially led many to assume that Kaby Lake G was paired with a lower power 15-watt “U” series chip. Kaby Lake G is instead based on an “H” part, which is rated at 45 watts and can run at 56 watts until it heats up.
Is it Polaris or Vega? It probably doesn’t matter
We reported earlier this year that although Intel branded Kaby Lake G with AMD’s newest and best graphics “Vega” brand, it appears to be based on AMD’s older stock of Polaris graphics cores used in the RX 580 series. Intel just spiced up Polaris with Vega elements, including high-bandwidth cache and HBM2 memory. Intel officials declined to comment.
So did Intel lie? Did it misrepresent something as Vega that’s actually Polaris? No. Branding is artificial. Intel could, for example, introduce a new Atom-based CPU and call it a Core i9 if it wanted to. (Yes, the fallout would be horrific, but that’d be on them.) In the end, it’s a custom GPU with a lot of advanced features.
Kaby Lake G Gaming Performance
Is Intel’s Kaby Lake-G good enough for gaming? The short answer is yes. Intel has said Kaby Lake G will comfortably compete with a GeForce GTX 1050 in gaming performance, and for the most part we find that to be true.
The longer answer is: It depends. As with all things, certain games and even certain parts of games will favor various features of a GPU, such as memory bandwidth or shader performance, as well as the actual architecture of the chip. In general, though, we’d say that the Radeon RX Vega M GL compares well to a GTX 1050 in performance.
Our first test is Futuremark’s 3DMark Sky Diver. It’s a popular, basic synthetic graphics test. As you can see, when compared to other GTX 1050 laptops as well as machines in its class, it does very well.
Going up against more typical workhorse laptops isn’t quite as fun as seeing how the Core i7-8705G stacks up against gaming laptops, so we ran a few games on the Spectre x360 15 as well. The first is the venerable Tomb Raider at 1080p resolution and set to the Ultimate preset.
We’ve found the circa-2013 Tomb Raider, like many older games, can be particularly sensitive to CPU performance. The results here speak well for the Core i7-8705G Kaby Lake: It easily outpaces a Core i5-7300HQ with GTX 1050 Ti and a Core i7-7700HQ with GTX 1050 GPU.
Middle-earth: Shadows of Mordor also agrees that the Radeon RX Vega M GL in the Kaby Lake G is a pretty decent chip. Middle-earth also tells us it ain’t no GeForce GTX 1060.
Although Kaby Lake G does well in Tomb Raider and Sky Diver, the reality of modern gaming is that sometimes it may not beat the competition. In fact, in Rise of the Tomb Raider, it’s actually slightly slower than a GeForce GTX 1050.
We could run through a few more gaming benchmarks, but you get the gist: It stacks up nicely against the GeForce GTX 1050 in most games.
Let’s turn back to 3DMark Sky Diver, where we tallied up pure graphics scores from various laptops that are actually “portable.” By portable, we mean laptops that are around five pounds, not beefy six- and eight-pound monsters. Portability limits you to a maximum of a GeForce GTX 1080 Max-Q laptop.
Clearly, when you’re looking at a GTX 1080 Max-Q or GTX 1070 Max-Q laptop, it’s a ton more performance. But those designs come with weight and battery costs. When you look at Kaby Lake G in the context of portable laptops, it does quite well.
On our chart below, we also highlighted three previous HP Spectre x360 15 laptops. If we assume that HP used the most powerful parts available at the time for the chassis, we’ve gone from Intel integrated graphics to GeForce 940MX to GeForce MX150 to Radeon MX Vega M GL.
From the graphics performance side of things, that’s pretty respectable. Sure, it’s not GeForce GTX 1060 by any stretch of imagination, but it’s still an impressive chip.
Keep reading for Kaby Lake G CPU performance benchmarks.
Kaby Lake G CPU Performance
As important as graphics performance is, we also want to assess the Core i7-8705G as a CPU. For that we broke out a few that we think it should compare well to, starting with the ubiquitous Core i7-7700HQ in the original Asus ROG Zephyrus laptop.
We also wanted to see how a higher-end chip would perform so we ran a few tests on a Lenovo Legion Y920 with its Core i7-7820HK in default stock mode (which was pretty conservative) and in its manual “turbo mode.” The Legion has a base default setting and an overclocked setting, which we also tested on. The last chip is the one that’s simply not fair, but it would be wrong to not include: The new 8th-gen 6-core Core i7-8750H in an MSI GS65 Stealth Thin.
One big caveat: Unlike reviews of desktop CPUs, a review of a laptop CPU isn’t just the CPU—it’s really the entire platform being judged. With a laptop you have no control over the cooling, the motherboard, or any of the other components.
Making this even more difficult is what each laptop maker decides to tune for. More noise? Less heat? More performance? Any of these can impact CPU performance greatly. Ideally, you’d want to be able to use the same platform for all of the tests, but that’s just not possible right now.
Still, that doesn’t mean comparisons are worthless. For the Core i7-7700HQ performance, for example, we made sure to do spot checks of the ROG Zephyrus against other Core i7-7700HQ results we’ve seen. For the most part, it’s right where that particular Kaby Lake CPU should be.
Cinebench R15 performance
Our first test is Cinebench R15. This 3D rendering test is almost entirely a CPU test and loves threads and clock speed.
Although the 6-core leads the way by a yuge margin, you have to respect the numbers of the Kaby Lake G Core i7-8705G as it outperforms both 7th-gen CPUs. The reason for this is simple: We’ve noticed Intel and vendors are far more comfortable pushing 8th-gen chips to higher clock speeds than the 7th generation.
The world isn’t about multi-threaded code, though, so we also run Cinebench using a single thread to simulate how the CPUs would perform in the vast majority of applications.
When measuring single-threaded performance, the number of cores no longer matters, so we see the 6-core Core i7-8750H come back down to earth. Just as we saw with multi-threaded loads, both 8th-gen CPUs have a significant clock speed advantage. The Core i7-8750H is on top, but nipping at its heels is the Core i7-8705G. Surprisingly, the Core i7-7820HK, even in its manual overclock mode, is running at lower clock speeds than the 8th-gen parts.
One weakness of Cinebench R15 is that it takes only a minute to run on fast CPUs. To see what happens to the CPU after a laptop heats up we turn to Handbrake, where we convert a 30GB 1080p file using the Android preset. This can take anywhere from a couple of hours on a dual-core CPU to 45 minutes on a quad-core CPU.
What we typically see on Core i7 CPUs is much flatter performance, once the high clock speed advantage it has burns off. While most Core i7 CPUs might run at 3.9GHz for a minute or three, they will usually perform 90 percent of the work at 3.6GHz or 3.5GHz.
The 6-core Core i7-8750H easily wins this thanks to its two additional cores. On the Core i7-8705G Kaby Lake G, we see it nearly dead-even with the Core i7-7700HQ CPU. Oddly, the performance of the Legion Y920 on default speed is pretty sedate. Push the turbo slider, though, and it’s off to the races.
It’s not just Handbrake and Cinebench that agree. We also ran the set of laptops through the Chaos Group’s V-Ray benchmark. It’s another multi-threaded benchmark that can run on the CPU or GPU. For this test, we chose the CPU test. The result again sees the 8th-gen Kaby Lake G ahead of the 7th-gen CPUs except when the Core i7-7820HK is overclocked. And yes, Core i7-8750H, you can stop showing off. We get it: 6 cores > 4 cores.
Next is VeraCrypt AES Encryption benchmark. The Core i7-7820HK finally squeaks out ahead on its default setting, but let’s just call this a tie all the way around (yes, except for you, 6-core Core i7), and a pretty good showing for a convertible laptop with Kaby Lake G inside.
Let’s cap this off with our final test, where we take Cinbench R15 and measure performance with the thread load manually set from one to eight. It’s no surprise that the Core i7-8705G is ahead under all loads over a 7th-gen Core i7-7700HQ.
One problem with the above chart is that it doesn’t actually show the percent increase, which might lead you to think the Core i7-8705G’s CPU performance edge is on the far right. The actual performance edge of the Kaby Lake G is on the far left.
TL;DR: It’s all clock speed
It’s no surprise that the 7th-gen CPUs aren’t that much different from the 8th-gen chips. What’s different is the clock speeds they run at. Intel has been using the 14nm process for so long now, it’s comfortable pushing far higher clock speeds. To get a feel for how much higher, we again took Cinebench and logged the clock speed of the CPU when it was 20 seconds into the test. This particular chart has the scaling set for readability, but you’re basically looking at a 200MHz across-the-board performance advantage.
What about thermal limitations?
You know Kaby Lake G uses Dynamic Power Sharing to help goose the CPU performance to top speeds, but you’re probably wondering how much of a limitation that is when there’s a GPU load, too. To find out, we ran the graphically intense Furmark stress test on the Spectre x360 15. We then ran Cinebench R15 and saw a pretty steep decline in its score. We don’t want to put a firm number on the performance because it never stabilized. That’s a bad thing, right?
That’s what we initially thought, until we ran the same load on an older Dell XPS 15 9560 with a Core i7-7700HQ and GeForce GTX 1050. In actual performance, both are somewhat similar when the CPU and GPU are tested alone. In a stress test of both, we actually saw the Core i7-8705G and Radeon RX Vega M GL manage its thermals far better than the Core i7-7700HQ and GeForce GTX 1050 combination. In fact, once it was heated up, the XPS 15 with traditional CPU+GPU performed far worse.
While this won’t apply to all Kaby Lake G laptops, it’s definitely a sign that we can’t assume the combined package will under-perform a traditional CPU+discrete graphics setup, because in some cases, it’s faster.
Overall, we’re pleasantly surprised by Kaby Lake G. We expected CPU performance closer to a low-wattage CPU, and GPU performance below a GTX 1050. Instead, we saw better performance than a 7th-gen Core i7 high-wattage chip, and GPU performance more on a par with a GTX 1050.
Remember, too, that the Spectre x360 15 is a 2-in-1 that converts to a tablet. We’ve seen a few 15-inch convertibles with high-power parts in them, and they generally under-perform traditional clamshell designs. With Kaby Lake G, you can apparently have your cake and still fold it back into a tablet, too.
Here’s why Nvidia (and AMD) should be scared of Kaby Lake G
As good as it is, Kaby Lake G isn’t going to shake up the CPU+GeForce scene today. But tomorrow, if there’s a Cannon Lake G or a Whiskey Lake G with more cores and better graphics, AMD and Nvidia should be worried.
What’s bad for Nvidia is how the integrated-CPU-and-GPU design concentrates power with Intel. If Intel buys the graphics chip and adds it, the laptop vendor is no longer making the choice, potentially freezing out Nvidia.
AMD isn’t sitting pretty either. Today Intel is buying Radeon graphics, but the company recently announced its intent to make its own discrete graphics. It’s entirely possible a future “G” chip will feature Intel discrete graphics, not AMD’s.
Today though, there are few takers of Kaby Lake G. In fact, only two vendors have shipped it: HP with the Spectre x360 15, and Dell with its XPS 15 2-in-1. Some we’ve spoken to have painted that as a failure of Kaby Lake G to catch on, while others have speculated politics to be the cause. Whatever the truth, it’s a shame, because applied the right way in the right laptop, Kaby Lake G is a road worth taking.